This recent article from the Journal of Chemical Education is an excellent overview of accidents that have happened involving flammable liquids. The authors report 164 children and educators have been injured over a 20 year period. The article also provides useful insights into why these accidents occur and measures necessary to prevent them.
In my opinion, this article is a “must read” for any science teacher considering bringing a sample of a flammable liquid into their classroom.
Link to article
Thanks for sharing this idea Milan !
While serious accidents causing catastrophic injury in high school science activities are rare, when they occur their human toll can be devastating. This post examines one potentially dangerous demo, its hazards and suggestions for safer alternatives.
The Rainbow Flame Demonstration:
Several of the most serious science accidents have resulted from the combustion of flammable liquids in teacher demonstrations like the rainbow flame demonstration. In this demo, metals salts are heated in a ceramic dish containing burning methanol. The flame colour observed is characteristic of the metal. Click on this link for an example of how this demo is sometimes done. Please note that the procedure used in this video, in our opinion, is unsafe, inappropriate for students of any age and NOT recommended for teachers.
Methanol vapours are extremely flammable. Furthermore, since the density of methanol is greater than that or air, methanol vapour can flow invisibly across surfaces like the demonstration desk and onto the floor towards unsuspecting observers. A flame, spark or even a hot surface can supply sufficient energy to ignite the vapour and create a sudden flash fire. The situation can be even more catastrophic if a nearby open container of methanol is present.
The Safer (and Better) Way:
Click here to download the complete article
Cells require a constant supply of glucose and oxygen to produce energy. As a result of this process, large quantities of waste carbon dioxide must be expelled from the cell. All materials involved in this reaction are either imported or exported through the cell membrane by diffusion.
In this demonstration, students soak agar “cells” containing phenolphthalein indicator in a solution of sodium hydroxide, NaOH(aq). Students observe the effect of cell volume and surface area on the extent of diffusion of the sodium hydroxide solution through the “cell”.
Click here to download the complete demo….
Steve Spangler’s Website
««« Written by Leila Knetsch…….
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Why Do Demonstrations?
I love doing demonstrations. I believe that they add so much to the science learning experience for a variety of reasons. First, I think that there is an element of surprise that is wonderful and hard to get in most circumstances. Second, a skilled demonstrator (such as Irwin Talesnick) can get students hooked but also push them to engage in critical thinking and predicting rather than just entertaining the students. Continue reading